The transfer of phospholipids between the ER and mitochondria is critical for mitochondrial biogenesis. Mitochondria cannot synthesize many of the lipids they require for membrane biogenesis and yet there is little or no vesicular trafficking to mitochondria. It is thought that lipids are transferred from the ER to mitochondria by a poorly understood nonvesicular mechanism. This transport has been proposed to occur at regions where the ER and mitochondria are closely apposed. In order to identify proteins required for phospholipids exchange between the ER and mitochondria we performed a genetic screen in collaboration with Dr. Chistopher Loewen at the University of British Columbia. We identified a conserved complex of ER proteins. We measured the exchange of phosphatidylserine between the ER and mitochondria in mutants missing a number of components of this complex. We found that lipid exchange slowed about 5 fold both in vivo and in vitro. This work is being prepared for submission.